Disclosed herein are methods and compositions to prepare non-porous, silicon-containing materials or films, such as but not limited to, stoichiometric or non-stoichiometric silicon oxide, silicon oxynitride, or silicon oxycarbonitride films, for use in various electronic applications.
Thin films of silicon oxide are commonly used as dielectrics in semiconductor manufacturing because of their dielectric properties. In the manufacturing of silicon-based semiconductor devices, silicon oxide films can be used as gate insulations, diffusion masks, sidewall spacers, hard mask, anti-reflection coating, passivation and encapsulation, and a variety of other uses. Silicon oxide films are also becoming increasingly important for passivation of other compound semiconductor devices.
Other elements besides silica and oxygen may be present in silicon dioxide films. These other elements may sometimes be intentionally added into the compositional mixture and/or deposition process depending upon the resultant application of the film or desired end-properties. For example, the element nitrogen (N) may be added to the silicon oxide film to form a silicon oxynitride film that may provide a certain dielectric performance such as lower leakage current. The element germanium (Ge) may be added to the silicon oxide film to provide a Ge-doped silicon oxide that may reduce the deposition temperature of the film. Still other elements such as boron (B) or carbon (C) may be added to the silicon oxide film to increase the etch resistance. Depending upon the application, however, certain elements in the film may be undesirable even at lower concentration levels.
For example, when silicon dioxide films are used as etch stop or simply as dielectric layer under photoresists of deep-ultraviolet (DUV), small amounts of nitrogen in the film may interact with the DUV photoresist, chemically amplifying the material properties of the photoresist or poisoning the photoresist and rendering a portion of the photoresist insoluble in the developer. As a result, residual photoresist may remain on patterned feature edges or sidewalls of the structure. This may be detrimental to photolithographic patterning process of the semiconductor devices.
Another example of nitrogen free silicon oxide films can be found in the application of anti-reflection coatings (ARC). The ARC suppresses the reflections off of the underlying material layer during resist imaging thereby providing accurate pattern replication in the layer of energy sensitive resist. However, conventional ARC materials contain nitrogen such as, for example, silicon nitride and titanium nitride. The presence of nitrogen in the ARC layer may chemically alter the composition of photoresist material. The chemical reaction between nitrogen and the photoresist material may be referred to as “photoresist poisoning”. Photoresist poisoned material that subjected to typical patterning steps could result in imprecisely formed features in the photoresist or excessive residual photoresist after patterning, both of which can detrimentally affect PR processes, such as etch processes. For example, nitrogen may neutralize acid near a photoresist and ARC interface and result in residue formation, known as footing, which can further result in curved or round aspects at the interface of the bottom and sidewalls of features rather than desired right angle.
For several applications, a plasma enhanced chemical vapor deposition process (“PECVD”) is used to produce silicon oxide films at lower deposition temperatures than typical thermal chemical vapor deposition (“CVD”) processes. Tetraethyloxysilane (“TEOS”) having the molecular formula Si(OC2H5)4 is a common precursor that can be used, in combination with one or more oxygen sources such as, but not limited to O2 or O3, for the PECVD deposition of silicon oxide films which have minimal residual carbon contamination. TEOS is supplied as a stable, inert, high vapor pressure liquid, and is less hazardous than other silicon-containing precursors such as SiH4.
There is a general drive to move to lower deposition temperatures (e.g., below 400° C.) for one or more of the following reasons: cost (e.g., the ability to use cheaper substrates) and thermal budget (e.g., due to integration of temperature-sensitive high performance films). Further for PECVD TEOS films, the gap fill and conformality may be relatively better at lower temperatures. However, the film quality of the PECVD TEOS film may be poorer because the films do not have a stoichiometric composition, are hydrogen-rich, have a low film density, and/or exhibit a fast etch rate. Hence, there is a need for alternative precursors with better performance than TEOS.